Re: new kernel oops in recent kernels

[Matthew Wilcox <matthew@wil.cx>]

On Sun, Mar 16, 2008 at 04:19:08PM +0100, Giuseppe Sacco wrote:
> testing latest kernels on SGI O2, I found this new kernel oops. It has
> been produced with kernel from linux-mips.org git of yesterday night.
> A very similar oops has been reported by others[0] using 2.6.22.

> CPU 0 Unable to handle kernel paging request at virtual address 0000000000000000, epc == 0000000000000000, ra == 0000000000000000

I'm not familiar with MIPS; is epc the program counter?  If so, this
would be a branch to 0.  That's somewhat confusing as I don't see any
function pointers used within sr_drive_status().  How accurate are MIPS
backtraces?

> Call Trace:
> [<ffffffff802460b0>] sr_drive_status+0x50/0xe8
> [<ffffffff8024bb84>] cdrom_ioctl+0x5f4/0x1208
> [<ffffffff80245c6c>] sr_block_ioctl+0x64/0xe8

It would be interesting to see a disassembly (objdump -dr
drivers/scsi/sr_ioctl.o) of sr_drive_status from say 0x40 to 0x60.

And if that calls a function, it would be interesting to put in printks
to figure out where we're dereferencing a null pointer.

-- 
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